High pressure pump



HIGH PRESSURE PUMP William Reginald Dermot Manning, St. Alban, EnglandOriginal application January 15, 1952, Serial No. 266,534. Divided andthis application July 12, 1954, Serial No. 442,851

1 Claim. (Cl. 103-158) This invention relates to pumps or compressorscapable of generating pressures greater than 1,000 atmospheres. Thisapplication is a division of my copending application Serial No.266,534, filed January 15, 1952.

Such pumps or compressors are used in chemical processes where fluidmaterials are subjected to high pressures, such as, for example, in thepolymerization of ethylene.

In pumps or compressors previously used for generating pressures of theorder of 1,000 atmospheres, or more, it has been found that there isserious risk of failure by fatigue. Such failures have been found tooccur at some irregularity of the section, such as the valve passages inthe cylinder head, or in the attachment of the head to the parallelportion of the cylinder. The occurrence of a failure at such highpressures might well have serious consequences, and one expedient whichhas been used to avoid such an occurrence is the replacement of thecylinder head after a predetermined number of strokes.

It is the object of this invention to reduce this danger very greatly.

According to the present invention, We provide a twostage reciprocatingpump or compressor capable of generating pressures greater than 1,000atmospheres comprising a cylinder embodying two axially-aligned pumpchambers of different diameters. A central wall integral with thecylinder separates the chambers and has a duct therethrough controlledby a non-return valve. A pair of spaced opposed stationary plunger-typepistons extends into the pump chambers from the opposite ends of thecylinder, and the latter is reciprocated to the pistons. A pump inletduct and a pump outlet duct are provided in the larger and in thesmaller pistons, respectively, and valves for the pump inlet and outletducts are located at the free or inner ends of the correspondingpistons.

If the available material is strong enough and the permissibledimensions are suiticient to contain the required pressure withoutproducing stresses (as calculated by the Lam hypothesis) that exceed thefatigue limit, simple monobloc cylinders can be safely used. For higherpressures, it may be necessary to employ reinforcing means for both thecentral wall and the side walls of the chambers, such as making thecylinders in concentric parts and shrinking them together, orwire-winding a core tube. Care must be taken with both reinforcingmethods, however, to avoid over-straining the material duringconstruction. For the former, the most economical design procedure isdescribed in Engineering, vol. 163, No. 4240, page 349, May 2, 1947, butcare must be taken to see that the residual stresses are not too highand this can be done by using the method described in En gineering ofDecember 8, 1950, in an article entitled Residual contact stresses inbuilt-up cylinders.

One form of our invention is illustrated in the accompanying drawingwhich represents a mid-sectional elevation of a two-stage pump orcompressor. The means for driving and supporting the pump are not shown.The reciprocating cylinder is built up from two axially nited StatesPatent 2,779,294 Patented Jan. 29, 1957 symmetrical concentriccomponents 1 and 2, component 2 having been shrunk onto component 1. Inthis type of pump or compressor, a compound cylinder is preferred, inorder to reduce tensile stresses about the oneway valve between thechambers, which is later described. The inner component 1 has twoaxially-aligned cylindrical chambers 9 and 10 separated by a centralwall 11 and connected by a duct 12 controlled by a conventionalnon-return valve 7. Chamber 10 is of larger diameter than chamber 9.Preferably, the side surfaces of the chambers curve smoothly into thecentral wall surfaces to eliminate stress-concentrating abrupt angles.

A piston 4 is located in chamber 9, and a seal is provided by the gland3. A second piston 6 is similarly located in chamber 10. The pistons 4and 6 have central ducts 13 and 14, respectively, for conveying fluidand conventional non-return valves 5 and 8, respectively, at their innerends. The two pistons 4 and 6 are fixed, and the cllinder is arranged toreciprocate relatively thereto.

-In operating the pump or compressor, when the cylinder moves from theright-hand end of its travel toward the left, valve 8 opens and fluid isdrawn into chamber 10. At the same time, fluid present in chamber 9 iscompressed and delivered through valve 5 into discharge duct 13. On thereturn stroke, as the cylinder moves to the right, fluid in chamber 16passes through valve 7 into chamber 9. Since chamber 9 is smaller thanchamber 10, this transfer will involve a rise in pressure of the fluidmaterial.

The compression which takes place in chamber 9 will lead to a rise intemperature in this part of the pump,

and it is desirable that a suitable cooling means (not shown) beprovided to prevent an excessive rise in temperature. This may take theform of a cooling jacket (not shown) surrounding the reciprocatingcylinder and through which cold water is passed.

The stresses in the neighborhood of the valve seats and ducts cannot becalculated with any degree of certainty, but, since they arepredominantly compressive, the risk of failure at these points owing tofatigue is very greatly reduced.

It is to be understood that the exact type of glands or valves usedwould be chosen according to the Working substance and the conditions ofoperation, e. g., pressure temperature, running speed. The requirementsof the glands are just the same as those that would have to be met in apump or compressor of conventional type.

I claim:

A two-stage reciprocating pump capable of generating pressures greaterthan 1,000 atmospheres comprising: a reciprocating cylinder of uniformexterior diameter having axially aligned bores of different diametersextending inwardly from the opposite ends of said cylinder and separatedby a central wall continuous with the side walls of said bores, theinterior junctions of said side and central Walls being curved toeliminate stress-concentrating abrupt angles; a one-piece reinforcingjacket coextensive with the length of said cylinder and shrunkthereonto; a duct in said central wall connecting said bores; anon-return valve controlling said duct; a pair of relatively-fixedplunger-type, stationary pistons mounted in said bores; a pump inletduct in the larger of said pistons and a pump outlet duct in the smallerof said pistons; and one-way valves controlling said inlet and outletducts at the inner ends of said pistons.

Dow May 4, 1886 Jewell Apr. 25, 1922

